That likely means dangerous flooding inland, as well as inundation of low-lying coastal areas by storm surges. “Our greatest concern is flooding,” Nicholas Petro, a National Weather Service meteorologist in Raleigh, North Carolina, told BuzzFeed News. His team tracks the weather for 13 counties in central and eastern North Carolina.

The initial concern away from the coast is flash flooding from excessive rainfall. The map above shows zones that the NWS forecasts face risks of flash flooding from rain in the next day.

“Wilmington is going to be ground zero,” Petro said, not only for rain, but storm surges and tremendously strong winds.

If the storm stalls in place for any length of time, much of the Carolinas is at risk. “There’s going to be increased flooding across both states extensively,” John Shelton, associate director of the US Geological Survey’s South Atlantic Water Science Center in Columbia, South Carolina, told BuzzFeed News.

“The threat is not just in eastern North Carolina,” Shelton said. “In western North Carolina, they are already wet. They’ve had increased rainfall for some time.”

In the days that follow the hurricane’s landfall, people living near rivers will face an additional and more persistent risk. Those rivers are likely to swell as they collect all that rain. The circles on the map show the longest available forecast — typically up to five days in the Carolinas — for flooding at stream gauges that are set up to monitor river heights.

The NWS forecasts are only available for the locations of stream gauges that have enough historical data to predict how a river will respond to anticipated rainfall, so provide at best a partial guide to where rivers may flood.

“Keep listening to local officials for evacuations,” Laurie Hogan, a hydrometeorologist with the NWS Eastern Region Headquarters in Bohemia, New York, told BuzzFeed News. “This really is a dangerous storm.”

UPDATE

Sep. 15, 2018, at 14:23 PM

Updated to reflect that map now shows flash flooding risk for Sept. 15

UPDATE

Sep. 16, 2018, at 13:58 PM

Updated to reflect the fact that the map is being automatically updated to show the current flash flooding and stream gauge flood risk.

Peter Aldhous is a Science Reporter for BuzzFeed News and is based in San Francisco. His secure PGP fingerprint is 225F B2AF 4B8E 6E3D B1EA 7F9A B96E BF7D 9CB2 9B16